The present invention relates to drilling rigs and more particularly the erection of a high floor modular drilling rig.
In the drilling of exploratory wells such as oilwells, rigs are employed which can be transported to a site and assembled in place to perform the drilling operation. It is necessary to provide elevated drill floors to provide a space thereunder for equipment such as safety devices, blowout preventers, and the like. The rig must have a base suitable to support the rig on infirm soil so that the weight of the rig and the drilling equipment will be distributed over the base area for transfer to the earth.
According to the present invention, a drilling rig has a base for placement on the ground at a well site with a floor structure supported on parallel spaced legs pivotally attached between a floor structure and said base for allowing said floor structure to move from a low position on said base to an elevated position above said base by rotation of said legs to a vertical position. A pair of strong back towers are provided one on each side of the base near midway the length thereof with sheave means supported at the top of each tower with the axes thereof transverse the length of the base. Sheaves on each side of said floor structure have cables passing successively each sheave on said floor structure and over sheaves on the towers. Hydraulic means on each side of said base powers the cables to pull the floor structure to an elevated position adjacent said towers.
Preferably a pair of sheaves are mounted on each side of the base over which each cable passes. The hydraulic means comprise cylinders mounted on the base each connected to two ends of each cable for pulling the cables through the sheaves to raise the floor structure.